webpack.config.js

const UglifyJSPlugin = require('uglifyjs-webpack-plugin');

module.exports = {
    development: {
        devtool: 'eval',
        module: {
            rules: [
                {
                    test: /\.js$/,
                    exclude: /node_modules/,
                    use: {
                        loader: 'babel-loader',
                        options: {
                            presets: ['env']
                        }
                    }
                }
            ]
        }
    },

    production: {
        module: {
            rules: [
                {
                    test: /\.js$/,
                    exclude: /node_modules/,
                    use: {
                        loader: 'babel-loader',
                        options: {
                            presets: ['env']
                        }
                    }
                }
            ]
        },
        plugins: [
            new UglifyJSPlugin()
        ]
    }
};